Manufacturing Method of Semi-Finished Piston with Inner Cooling Channel through Liquid Extrusion Process

ABSTRACT

This invention has provided a manufacturing method of semi-finished piston with inner cooling channel through liquid extrusion process, including the following steps: a) produce a wear-resistant cast iron ring with coupling hooks and a common salt and corundum dissoluble core with convex edges; b) fix the wear-resistant cast iron ring in the casting moulds after being aluminized; c) fix the dissoluble core after being pre-heated on the wear-resistant cast iron ring with coupling hooks and convex edges; d) fill in the casting mould with aluminum alloy liquid, compressing and molding. The dissoluble core can be accurately fixed in the casting mould through coupling hooks and convex edges. When the semi-finished piston has been manufactured into finished product, it shall be characterized by high compactness and high mechanical property resulted from liquid extrusion technology. Meanwhile, because of the cooling channel, the temperature in the combustion chamber of the head and ring groove is reduced, the load capacity of the piston is greatly improved, and the manufacturability becomes better.

CROSS REFERENCE TO THE RELATED PATENTS

This application claims the priority benefit of the Chinese patent application No. 200510044839.6 filed on Oct. 8, 2005.

FIELD OF THE INVENTION

The present invention has provided a kind of manufacturing method of semi-finished piston, especially the one with inner cooling channel.

BACKGROUND OF THE INVENTION

At present, engines used intrucks, engineering machinery, railvehicles and ships are developed into that of high efficiency and heavy load with increased strength and strict discharge requirement. Temperature of the piston head can be effectively reduced and performance of the engine can be greatly improved by adding an inner cooling channel on the head of the piston. Liquid extrusion technology can make the structure much more compact and improve mechanical property of the piston. Therefore, the service performance can be greatly enhanced by combining these two kinds of technologies. The inner cooling channel is formed by fixing dissoluble cores at the head of semi-finished piston, and then washing them away. However, being limited by extrusion technology, the dissoluble cores can not be positioned and fixed by the mould itself. At present the material of cores used to form the inner cooling channel is salt. During the manufacturing procedure, aluminum alloy liquid can immerge into the core under high temperature and high pressure. When the semi-finished piston has been manufactured, dissoluble cored can not be totally washed away, which may affect the cooling effect in the future. Therefore, the manufacturing method of semi-finished piston with inner cooling channel through liquid extrusion process has not been realized. Only those semi-finished pistons without inner cooling channel can be produced by liquid extrusion method, while semi-finished pistons with inner channel can only be produced by using ordinary manufacturing method.

SUMMARY OF THE INVENTION

This invention aims to provide a manufacturing method of semi-finished piston with inner cooling channel through liquid extrusion process to realize the improvement of structural compactness of piston as well as the formation of inner cooling channel.

The manufacturing method of semi-finished piston with inner cooling channel through liquid extrusion process includes the following steps:

-   a) produce a wear-resistant cast iron ring with coupling hooks and a     common salt and corundum dissoluble core with convex edges; -   b) fix the wear-resistant cast iron ring in the casting mould after     being aluminized; -   c) fix the dissoluble core, after being pre-heated, on the     wear-resistant cast iron ring with coupling hooks and convex edges; -   d) fill in the casting mould with aluminum alloy liquid, compressing     and molding.

By using this manufacturing method, the dissoluble core can be accurately fixed in the casting mould through coupling hooks and convex edges. Compared with other dissoluble cores, the one made of common salt and corundum is of low thermal coefficient of expansion and dimensional stability. The intensity and density are high. And it cannot soak into melted aluminum liquid. The aluminum alloy can not immerge into the core under high pressure and high temperature, which will be better for it to be cleared away when forming the inner cooling channel. It has high ability to resist chilling and heating with better manufacturability. When being washed away, the salt can be dissolved quickly. When the semi-finished piston has been manufactured into finished product, it shall be characterized by high compactness and high mechanical property resulted from liquid extrusion technology. Because of cooling channel, the temperature in the combustion chamber of the head and the ring groove shall be reduced, and carrying capacity of the piston shall be greatly improved. It can meet the performance requirements of high-power and heavy-load engines. Meanwhile, the manufacturability shall be better.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a sketch drawing of the semi-finished piston manufactured by the method of present invention.

FIG. 2 is a sketch drawing of the finished piston made from the semi-finished piston. FIG. 3 is a front cross section view of the wear-resistant cast iron ring.

FIG. 4 is a top view of the FIG. 3.

FIG. 5 is a front cross section view of the dissoluble core.

FIG. 6 is a top view of the FIG. 5.

FIG. 7 is a perspective view of the dissoluble core fixed on the wear-resistant cast iron ring.

FIG. 8 is a cross section view of the wear-resistant cast iron ring fixed on the casting mould.

Numbers in the FIG: 1—combustion chamber, 2—head; 3—wear-resistant cast iron ring; 3-1—coupling hook; 4—dissoluble core; 4-1—convex edge; 5—ring edge; 6—pinhole; 7—skirt; 8—inner cooling channel; 9—internal mould; 10—hold-up ring; 11—external mould; 12—bottom mould.

DETAIL DESCRIPTION OF THE INVENTION

The present invention will be described in detail with reference to the attached drawings.

The above-mentioned dissoluble core (4) is produced as follows:

-   a) crush the common slat and corundum until they can pass 80˜120     screen, and heat them to 450˜550° C. to remove moisture and other     volatile impurities; -   b) distribute corundum 20˜40% weight per share, and salt 60˜80%     weight per share, and then mix them up; -   c) put the mixture in the mould, compressing and molding; -   d) process the surface of the molded dissoluble core by the lathe; -   e) bake the lathe processed dissoluble core in baking furnace, and     then take it out.

Dissoluble core with common salt as cementing medium and corundum grain as basal body can be produced according to the above methods. When semi-finished piston has been produced, drill an oil inlet/outlet hole, connected with inner chamber of the piston, at the lower part of the core. Fill water into the hole letting the salt be dissolved and the corundum grain be washed away to form inner cooling channel (8). When baking the dissoluble core in baking furnace, the temperature shall be a little bit higher that used for present salt core.

The above-mentioned corundum can also be made of barium oxide, zirconia or other similar materials.

The number of coupling hooks on wear-resistant cast iron ring and convex edges on the core shall be three or more than three respectively. Compressing and molding technique is the same as that in the present liquid extrusion technology. And aluminizing treatment is the same as that in present technology.

As illustrated in FIG. 1, semi-finished piston produced by liquid extrusion technology comprises a head (2), a ring edge (5) and a skirt (7). There is a pinhole (6) on the skirt, and a combustion chamber (1) on the head. The first ring groove is composed of a wear-resistant cast iron ring (3) with coupling hooks (3-1) inside. The cast iron ring is connected with the dissoluble core through the coupling hooks and convex edges on the dissoluble core (4) inside the semi-finished piston.

As illustrated in FIG. 8, the casting mould is composed of internal mould (9), hold-up ring (10), external mould (11) and bottom mould (12). Semi-finished piston produced by this method can be manufactured into finished piston shown in FIG. 2 through conventional T6 heat treatment and further machining.

This invention has only described and illustrated its typical form, based on which people with common knowledge in this field can make many proper diversifications and modifications. For example, high performance piston with inner cooling channel, wear-resistant cast iron ring as well as combustion chamber of partially strengthened composite material can be produced by using this invention. 

1. A method of manufacturing semi-finished piston with inner cooling channel through liquid extrusion process comprising: a) producing a wear-resistant cast iron ring with coupling hooks and a common salt and corundum dissoluble core with convex edges; b) fixing the wear-resistant cast iron rings in a casting mould after being aluminized; c) fixing the dissoluble cores, after being pre-heated, on the wear-resistant cast iron ring with coupling hooks and convex edges; d) filling in the casting moulds with aluminum alloy liquid, compressing and molding.
 2. The method of claim 1 wherein the dissoluble core is manufactured as follows: a) crush the common slat and corundum until they can pass 80˜120 screen, and heat them to 450˜550° C. to remove moisture and other volatile impurities; b) distribute the corundum 20˜40% weight per share, and the salt 60˜80% weight per share, and then mix them up; c) put the mixture in a mould, compressing and molding; d) process the surface of the molded dissoluble core; e) bake the processed dissoluble core in a baking furnace, and then take it out.
 3. The method of claim 1 wherein the corundum is barium oxide or zirconia.
 4. The method of claim 2, wherein the corundum is barium oxide or zirconia. 